Food and diet relationships of Parachanna obscura (Gunther) and Clarias gariepinus (Burchell) in a newly impounded Osinmo reservoir, Ejigbo, Nigeria

The food and diet of two economically important freshwater fish species, Parachanna obscura and Clarias gariepinus were examined in Osinmo reservoir. Gill-net, cast-net and traps were the fishing gears used to collect fish specimens. Morphometric parameters of each fish were taken. Stomach fullness was noted and each stomach preserved in 4% formalin. Frequency of occurrence and Numerical methods was used to analyse the stomach contents of each fish. The study observed by frequency of occurrence that insects, fish, and algae, constituted 73% of the stomach contents of P. obscura throughout the sampling period. Similarly the stomach contents of C. gariepinus were dominated to the tune of 79% by detritus, mud, fish, algae, insects and diatoms. Slight variation in food items was observed during the dry and rainy seasons. The percentage of non- empty stomachs in dry and rainy seasons increased from 80% to 89% in P. obscura and from 74.6% to 83.4% in C. gariepinus. The two species of fish fed on many related food items and Schoener overlap index values of 0.05 and 0.02 indicated no diet overlap and competition in dry and rainy seasons

Preliminary evaluation of some aspects of the ecology (growth pattern, condition factor and reproductive biology) of African pike, Hepsetus odoe (Bloch 1794), in Lake Eleiyele, Ibadan, Nigeria

Abstract A preliminary investigation of length-weight relationship, condition factor and reproductive ecology of African pike fish, Hepsetus odoe, was conducted between June to August 2010 in Lake Eleiyele. A total of 90 samples of the fish species were caught by fishermen using gill nets. The results obtained showed that fish species had isometric growth pattern (contrary to negative allometry expected) with the growth exponent, b value of 2.64, that is not statistically different from 3 and with high statistical power of 0.866 when tested. The mean condition factor, K, was found to be 2.6, indicating that the fish species were in good condition in the study area. For reproductive biology, mean fecundity and gonadosomatic index were found to be 1349 eggs and 3.53% respectively. This study was necessary to fill the knowledge gap and provide information for management and conservation of the investigated species in the lake system. This study recommended that further research needs to be conducted because the sampling was carried out in the rainy season period and within a quarter of a year